The primary objectives of this research project concern the delineation of the precise mechanisms of cooperative interactions between thymus-derived (T) lymphocytes and the bone marrow-derived (B) precursors of antibody-forming cells in the development of immune responses. These studies are focused primarily on the interactions between carrier-specific T cells and hapten-specific B cells in immune responses to hapten-carrier conjugates both in vivo and in vitro, and are ultimately directed toward the adaptation to potential therapeutic applications the capacity to greatly enhance or suppress humoral and cellular immune responses to a variety of antigens. Toward this end, we are also concerned with studies designed to develop a better understanding of the sub- or intracellular events involved in mechanisms of cell triggering and specific immunological tolerance.